This invention relates to very-large, heavy-duty, radial pneumatic tires and, more particularly, to a novel and highly-effective pneumatic tire of that kind having a special reinforcement.
U.S. Pat. No. 3,789,900 discloses a very-large, heavy-duty tire for construction equipment having a carcass reinforcement substantially formed of radial cords or cables and, radially outward of the carcass reinforcement, a crown or tread reinforcement which comprises at least two superimposed plies of cords or cables that are parallel in each ply but crossed from one ply to the other. The tread reinforcement is narrower than the tread, has a slightly curved meridian profile, and restrains the carcass reinforcement on the radially outer side. Under the effect of this restraint, the carcass reinforcement, in the region covered by the tread reinforcement, assumes a meridian profile which is less curved than the normal equilibrium profile while in the region of the shoulders of the tire it assumes a meridian profile which is more curved than the normal equilibrium profile.
Under the action of the inflation pressure, the carcass reinforcement, because of the radial orientation of its cords or cables, tends to assume a pronounced meridian curvature. The tread reinforcement, under the same conditions, tends, as a result of the relatively longitudinal orientation of its cords (at most 30.degree. with respect to the longitudinal direction of the tread), to assume a meridian curvature which is definitely less than that of the carcass reinforcement.
The patent mentioned above discloses, radially on the inside of the carcass reinforcement, in each of the two zones of the shoulders where the crown reinforcement imposes a strong curvature on the carcass reinforcement, at least one auxiliary ply of elastic cords or cables inclined by at most 30.degree. with respect to the cords or cables of the carcass reinforcement.
Such an arrangement attenuates the restraining force exerted by the crown reinforcement while maintaining, within the region of the shoulders, the pronounced curvature of the carcass reinforcement caused by the placing under tension of the cords or cables arranged radially inward of the carcass reinforcement.
U.S. Pat. No. 2,930,425 discloses a tire having a carcass reinforcement including at least two radial cord plies extending from bead to bead and a tread reinforcement formed by at least one ply of conventional cords oriented at an angle of 90.degree. with respect to the radial direction and disposed radially inside the tread, and by at least two conventional plies formed of cords oriented at angles between 20.degree. and 60.degree. with respect to the radial direction, the last-named plies being disposed between or radially inside the carcass reinforcement plies and having an axial width that is greater than the width of the tread.
The object of this structure is to reduce tread wear by separating both functionally and structurally the tread-reinforcing plies provided to reduce the longitudinal and the transverse creeping of the tread on the road.